Process of making amino-anthraquinones



t d States Paten No Drawing.- Application January 9, .1952;

Serial No. 265,728

Glaims priority, application'switzerlfind January 24; 1951 3 Claims. (Cl. 260-"371) Tl ie present'invention provides a process for the reduction of nitroanthraquinones. The .nitroanthraquinone's subjected t'o the reduction are those which contain the nitrogroup in anon-position of one of the-benzene rings ofthe anthraquinone nucleus and an alkyl siilfone grou ina fi position of the other benzene ring of the anthra quin'one nucleus, andth'e reductiorris carried"out"with water solublesalts of hydrosulfuric acid.

As' nitronanthraquinones to be subjectedto ther'educ; new there" come into consideration more 3 especially 1-nitro-6- and -7-alkyl-sulfone-anthraquinonesg of which tlie"anthraquinone nuclei are freefromfurther'substituents and of which the alkyl group contains 'only a-few; foi' example; 1'5 carbon atoms, the'ca'rbon chain being straighv or branched. These nitro-alkylsiilfone arithra quinones are new. They can be made by'nitratingfl alkyl sulfoneantlfraquinones, for example, with" amiXture' of sulfuric etcidandnitric acid. There are-'ohtained mixtu'res of-is'omeric'nitro compounds, which consisrmainly of i l nit 'ro-6 and -7-alky1sulfone-anthraquinones. While in cert'ain' cases, for example, inthe case ofl-nitro-6 methyl sulfone anthraquinone it is easy, and in'flfe-ca'se of 1 nitro=7 methyl-sulfone-anthraquinone' somewhat more difiicult', too'btain pure unitary nitro compounds from the isomeric mixt u're by separating-them from the "nitration miXtiIre by diIutiOn with water, redissoluti'on in'concen trate'd sulfuric acid and precipitating in succession l nitro- 6-me'thyl sulfone-anthraquinone and 1-nitro-7-'methy1 sul fone anthraquinoneby the addition of water, it is'difficul't in this manner to prepare other unitary-1 nitro 6 and -7-'a'lk yl sulf'one anthraquinones, for example, the iso'-- propyl compoun'ds;

Therpre'sentinvention makes it possible toobtain fi'om' such?- isomeric mixtures resulting from the nit-ration of" fl alkyl sulfoneanthraquinones, and with whiclitlreabove deseribed methodof separation is impracticableg-unitary 1-amino-6-alkyl sulfone-anthraquinones to be separated from the other reduction products and then to obtain fromftheresidual reduction mixture the*l- -amino-'7-alkylsulfne anthraquinones.

'Ihe mannerin which 1-nitro-6- and -7-alltyl sulfone anthraqiiinones react'with water-soluble salts of hydrosulfuricacidin an aqueous medium is as follows: At a raised-temperature, for example, at the boilingtempera ture onthe' reaction mixture, generally not onlyTis'the n'itm group reduced to an amino group but also the alkylsulfone group' is exchanged fora mercapto group.

However, at a suitably low reaction temperature l-nitr mfi 'and 7 alkyl-sulfone-anthraquinone donot act the'sarne manner. In the case of the latter compound the'abov'e' mentioned conversion of the alkyl sulfone 'group intoa mercapto'group occurs in addition'to thereduction of thenitro group, but with the formercotnpound th'e alky'l sulfone group remains unchanged, andonly the nitfo group is reduced. If, therefore, an is'ome'ric' mixture consistifigprincipally of 1-nitro-6- and -7-alkyl-sult'on'eanthraquinonesis reduced in this manner, .a1-arnin0-6-' 2,738,354 Patented Mar. 13, 1956 2 allyl-sulfone anthraquinone is obtained" as a residue. After' separating the latter, the 1 -amino7'-mercap'toanthraquinonedissolved in the filtrate inthe form of an alkali metal or ammonium salt can be separated, for example, by theadditionof-an acid or a salt:'

As stated'above, the're'may befused as'the starting'rnaterial' in the reduction proce'ssof this invention isomeric mixtures obtained by the nitration of fl-alkyl-sulfoneanthraquinones. As examples of B-alkyl-sulfone='anthra quinonestheremaybe' mentioned ,B-methyl p-ethyl fi-n propyl, fi-isoprop'yl or fl n but'yl sulfone-anthraquino'ne. Y

The water-soluble salts of'hydrosulfuric acidserv'ing' as re'ducingagents-in the present process may be'-sulfi'des"or advantageously hydro-sulfides; As examples-there may bementioned ammoniumsulfides, hydro sulfidesof alka line earth 'metals, suchas calcium "hydrosulfide' and alkali metal sulfides" such'as sodium sulfide. Especially advantageous are'alkali metal hydro-sulfides, forexample, sodium-hydrosulfide.

Thereduction is advantageously carried out in an aque-' o'u's medium. Since the nitro alkylsulfone-anthraqui nones to be reduced and; insofar as the alkyl sulfone'gr'oup is 'retained during' the reduction, alsothe reduction prod nets are water-insoluble it isadvisabletouse thenitro compounds in a very finely;dispersed condition.

The l-amino-7-mercapto=anthraquinones, which are obtained-:asstatedabove in the reduc'tion of a' mixture consisting of l-nit'ro-6- and -'7-alkyl sulfoneanthraquinone;

may. be-treated with the usual alkylating'ag'ents, and the resulting 1-.arnino-7-alkyh mercapto-anthraquinon'es con vetted "by oxidation,- for example; .by. meansof peroxides, especially hydrogem peroxide; into thecorresponding 1-amino 7-alkyl-sulfone-anthraquinones;

As will be understood from the foregoingzdescription, the present invention enables L-a'mino-G- and --7-alkyl-sul fone-anthraquinone to be obtained 1 practically 'free from isomers. If desired, there may also be made 1-amino-6 alkyl-sulfone-anthraquinones which contain an alkyl group other than thatpresent in-the' l-nitro-6-alkyl-sulfone anthraquinone or amixture o'f 1-nitro-6- and -7-a1ky1- sulfone-anthraquinone' used'as starting. material. For'this purpose: for example, 1-nitro-6-methyl-sulfone=anthraquinoneis reduced in the nianner described above to l-amino-6+mercapto-anthraquinone; or l-amino-fi rnethyl'- sultone-anthraquinone obtained bythe-reduction of a mixture of: l-nitro-6- and -7-methyl-sulfone anthraquinone and-then isolated, is converted into1-amino-6 mercaptoanthraquinone, the mercapto group is treated with an' alkylating agent- (other than: a methylating. agent) and finally the alkyl mercapto'group is-oxidized'to the cor're sponding alkyl sulfo'n'e group;

The products ofthe invention are new. They are aminoanthraquinones, which contain theamino group in an oz-pOSitiOn of 1 one 'of the' benzene rings of the anthra quinone nucleus and-analkyl-s'ulfone group or an alkyl" mercapto group in a fi-position of 'the'other benzene'ring of 'the anthraquinone nucleus. These'newcompounds are valuable intermediate products; for example, for the manufacture of vat dyestuffs ofthe anthraquinone series;

The following; examples '5 illustrate the invention, the parts and percentages being by weight:

Example '1 229 parts of Z-methyl-sulfone-anthraquinone are dissolved" in 910 parts of sulfuric monohydrate at room temperature. The whole is-then-heated to '80 C. and a' mixture of 64 parts of nitric acid of -96 percent strength and 64 parts of sulfuric monohydrate is introduced drop,- wise, -wh ile stirring, in 5 the course of 1 hour. After stirring for 6 hour at 100 (3., thelmix-ture is allowed to cool, 260 parts of water are-'added 'cautiously, thewhole is filtered with suction, and the filter residue is washed with sulfuric acid of 70 per cent strength, and washed free from acid with water. The filter cake is ground well with 1630 parts of water and after the addition of 6600 parts of water and 1265 parts of sodium hydrosulfide solution of 30 per cent strength the whole is stirred at 64-67 C. for 5 hours. After cooling, the mixture is filtered with suction, and the filter residue is washed with water and dried. After recrystallization once from ortho-dichlorobenzene there are obtained red needles which consist of pure l-amino-6-methyl-sulfone-anthraquinone. The filtrate containing sodium hydrosulfide is mixed with a large quantity of sodium chloride, and after allowing the mixture to stand for 24 hours at -5 C., the precipitate is separated by filtering with suction. The sodium salt of 1-amino-7-mercapto-anthraquinone, after being washed with sodium chloride solution, may be dissolved in water and methylated with methyl iodide. After recrystallization from nitrobenzene the reaction product forms orange-brown crystals, which dissolve with a cornflower blue coloration in concentrated sulfuric acid. The product is pure 1-amino-7-methyl-mercaptoanthraquinone. It can be oxidized to l-amino-7-methylsulfone anthraquinone, for example, in acetic acid with hydrogen peroxide. When recrystallized from nitrobenzene, l-amino-7-methyl-sulfone-anthraquinone forms brown crystals, which dissolve in concentrated sulfuric acid with a weak yellow-brown coloration.

Example 2 15 parts of l-nitro-6-methyl-sulfone-anthraquinone are finely pulverized and suspended in 600 parts of water. After the addition of 82 parts of sodium hydrosulfide solution of 30 per cent strength, the whole is stirred for hours at 64-67 C., filtered with suction while hot, and the filter residue is washed with water and dried. By recrystallization from ortho-dichlorobenzene there is obtained 1-amino-6-methyl-sulfone-anthraquinone crystallizing in red-brown needles.

1-nitro-6-methyl-sulfone-anthraquinone is prepared as follows:

229 grams of Z-methyl-sulfone-anthraquinone are slowly introduced into 480 grams of sulfuric monohydrate at room temperature. While stirring, the temperature is raised to 80 C., and then a mixture of 64 grams of nitric acid of 96 per cent strength and 64 grams of sulfuric monohydrate is introduced dropwise in the course of 1 hour, whereupon the temperature rises to 90 C. After stirring for a further /2 hour at 100 C. the whole is allowed to cool, and then cautiously introduced into a mixture of ice and water, the whole is then filtered with suction, and the filter residue is washed until neutral and dried. In order to separate the isomers, for example, 130 grams of the nitration product are introduced at C. into 1 kilogram of sulfuric acid of 95 per cent strength and the whole is stirred until dissolution is complete. 188 grams of sulfuric acid of 50 per cent strength are then introduced dropwise at l015 C. in the course of about /2 hour, and the whole is stirred for a further 3 hours at Ill-12 C. The precipitated l-nitro-6-methyl sulfone-anthraquinone is separated by filtering with suction, washed with sulfuric acid of 88 per cent strength and poured into a mixture of ice and water. The resulting suspension is filtered with suction, and the filter residue is washed until neutral and dried.

Example 3 68 parts of l-nitro-6-methyl-sulfone anthraquinone (see Example 2) are finely pulverized and suspended in 2800 parts of water. The suspension is then heated to the boil, mixed with 380 parts of sodium hydrosulfide solution of 30 per cent strength and stirred for 2 hours at l0O10l C. After air has been blown through the cooled solution for a few hours, the resulting crystalline precipitate is separated by filtering with suction. The

resulting sodium salt of 1-amino-6-mercapto-anthraquinone dissolves in water and can be methylated with methyl iodide. The methylation product crystallizes from trichlorobenzene in the form of red-brown crystals and is pure 1-amino-6-methyl-mercapto-anthraquinone. The compound dissolves in concentrated sulfuric acid with a somewhat less pure blue coloration than the 1-amino-7-methyl-mercapto-anthraquinone described in Example 1.

Example4 30 parts of 1-nitro-7-methyl-sulfone-anthraquinone are finely pulverized and suspended in 1200 parts of water. After the addition of 165 parts of sodium hydrosulfide solution of 30 per cent. strength the whole is stirred for 5 hours at 6467 C. The Whole is then cooled, and mixed with 160 parts of sodium chloride, stirred for a few hours at 0-5 C., filtered with suction, and the filter residue is washed with sodium chloride solution of 10 per cent. strength. The filter cake (the sodium salt of 1-amino-7-mercapto-anthraquinone) is dissolved in 800 parts of water, and the solution is mixed with 10 parts of methyl iodide and stirred for 3 /2 hours at room temperature. The reaction product, which is separated by filtering with suction, after recrystallization from nitrobenzene is in the form of brown-orange crystals which dissolve in concentrated sulfuric acid with a cornflower blue coloration. It is pure 1-amino-7-methyl-mercaptoanthraquinone.

1-nitro-7-methyl-sulfone-anthraquinone may be prepared as follows:

229 parts of 2-methyl-sulfone-anthraquinone are dissolved at room temperature in 480 parts of sulfuric monohydrate. Nitration is carried out in the course of 1 hour with a mixture of 64 parts of nitric acid of 96 per cent. strength and 64 parts of sulfuric monohydrate at C. After stirring the whole for /2 hour at 100 C., it is allowed to cool, introduced into ice water, filtered with suction, and the filter residue is washed neutral and dried. 130 parts of the resulting isomeric mixture are dissolved at room temperature in 1000 parts of sulfuric acid of per cent. strength. The whole is then mixed with 188 parts of sulfuric acid of 50 per cent. strength while stirring, and stirring is continued at 10-15 C. for 4 hours. The whole is then filtered with suction, and the filter residue is washed with 300 parts of sulfuric acid of 88 per cent. strength. The resulting filtrate is mixed at 5-12" C. while stirring, with water until the concentration of sulfuric acid reaches 80 per cent. After stirring for 3 hours, the mixture may be filtered with suction, and the filter residue washed with sulfuric acid of 80 per cent. strength and with water and dried. The resulting crude l-nitro-7-methyl-sulfone-anthraquinone dissolves in concentrated sulfuric acid with a feebly yellowish coloration.

Example 5 monohydrate at 80-83" C. After stirring the mixture for a further /2 hour at C., it is allowed to cool and dried. The powdered residue is dissolved in 3000 parts of sulfuric acid of 98 per cent. strength. The whole is diluted by slowly introducing dropwise water or dilute acid While stirring, until the concentration of the acid is 75 per cent., the mixture is then stirred for 2 hours at 0-5 C., filtered with suction, and the filter residue is washed with sulfuric acid of 75 per cent. strength, then washed until neutral and dried. 14.6 parts of the resulting nit'ro-isopropyl sulfone-anthraquinone mixture are,

ground overnight with 40 parts of water. After the addition of 660 parts of water and 150 parts of sodium hydrosulfide solution of 30 per cent. strength, the whole is stirred for 1% hours at 90 C., filtered with suction while hot and the filter residue is washed until neutral and dried. By recrystallization from ortho-dichlorobenzene 1-amino-fi-iscpropyl-sulfone anthraquinone is obtained in the form of flat red needles which melt at 218220 C. The analysis of the product is as follows: Carbon calculated 62.00 per cent, found 61.81 per cent., hydrogen calculated 4.59 per cent., found 4.47 per cent., nitrogen calculated 4.2 per cent., found 4.1 per cent.

What is claimed is:

1. Process for the reduction of nitroanthraquinones, which comprises reducing, in an aqueous medium at a temperature below the boiling point of the reaction mixture, with a water-soluble salt of hydrosulfuric acid a member selected from the group consisting of (a) a nitro-anthraquinone which contains the nitro group in an a-position of one of the benzene rings of the anthraquinine nucleus and an alkyl-sulfone group in a B-position of the other benzene ring of the anthraquinone nu cleus and (b) an isomeric mixture of nitro-anthraquinone alkylsulfones as defined under (a).

2. Process for the reduction of nitroanthraquinones, which comprises reducing, in an aqueous medium at a temperature below the boiling point of the reaction mixture, with a water-soluble salt of hydrosulfuric acid a nitro-anthraquinone of the formula N02 H l O alkyl l wherein the alkyl-SOz-group is bound in a fl-position of the benzene ring marked I of the anthraquinone nucleus and the alkyl group contains at the most 5 carbon atoms.

0 alkylg and 0 alkylg wherein the alkyl group contains at the most 5 carbon atoms and recovering from alkaline aqueous solution the 1-amino-anthraquinone-6-alkylsulfone which is insoluble in said solution.

References Cited in the file of this patent UNITED STATES PATENTS 2,176,630 Klein Oct. 17, 1939 2,434,765 Grossmann Ian. 20, 1948 FOREIGN PATENTS 72,453 Switzerland May 16, 1916 263,843 Great Britain Apr. 5, 1928 

1. PROCESS FOR THE REDUCTION OF NITROANTHRAQUINONES, WHICH COMPRISES REDUCING, IN AN AQUEOUS MEDIUM AT A TEMPERATURE BELOW THE BOILING POINT OF THE REACTION MIXTURE, WITH A WATER-SOLUBLE SALT OF HYDROSULFURIC ACID A MEMBER SELECTED FROM THE GROUP CONSISTING OF (A) A NITRO-ANTHRAQUINONE WHICH CONTAINS THE NITRO GROUP IN AN A-POSITION OF ONE OF THE BENZENE RINGS OF THE ANTHRAQUININE NUCLEUS AND AN ALKYL-SULFONE GROUP IN A B-POSITION OF THE OTHER BENZENE RING OF THE ANTHRAQUINONE NUCLEUS AND (B) AN ISOMERIC MIXTURE OF NITRO-ANTHRAQUINONE ALKYLSULFONES AS DEFINED UNDER (A). 